Importance of User Interface:-
I recently revisited the livejournal website and suddenly found it very interesting. Community, friends, FOF (Friends of Friends) so many useful features to be used. Those are totally lacking in my blogger account because it's not community oriented. The stats show that I am a member of LiveJournal since Feb 2001!!
What was the reason I did not used it for the last 3 years?
I myself don't believe the answer. But I think it's the only reason. The User Interface (or page layout), at that time was not intuitive or cool! The default journal entries page still have no links to very important features like login, search, subscribe RSS, about me, etc. You see all these links only if you are logged in and go to the profile page of a user.
Here is how the old design used to look like.

And here is the new, decent design.

This fact has raised a question: is the design really so important?
The answer is YES. Microsoft, with the help of user friendly design, gained the market share which was dominated by DOS and other UNIX like clones of operating systems which were (And still are) better than Windows.
I bought a http://quickbase.com account. I recommended the http://cgiscriptshop.com to everyone who were using Mysql. The reason? Simply better design (and not necessarily more functions or features).